The present invention relates to a device comprising a suspension system, which suspension system comprises a first part to which a mass is applied, a second part as well as at least one air spring arranged between the first part and said second part, at least one additional volume means for air being provided, the volume of which can be connected to a volume of the air spring in a controlled manner, as well as a control means for connecting the volume of the additional volume means.
Devices comprising a suspension system which has an additional volume means are known from the prior art. If required, in such devices which are already known from the prior art, the additional volume means can for example be manually connected and/or disconnected in order for it to be possible to set a force/displacement characteristic line of the air spring. In this case, “force/displacement line” refers to a characteristic line of the air spring, in which a resilience of the air spring is plotted against a deflection displacement and/or rebound displacement of the air spring in a two-dimensional coordinate system.
If, for example, the volume of the additional volume means is connected to the air spring, then this makes it possible to set the suspension properties to a softer damping of the air spring, whereas if the additional volume means is disconnected from the air spring, deflection is harder. In other words, if required, a force/displacement characteristic line of the air spring can be set by a connection or disconnection via the additional volume means without the air pressure in the air spring being modified. Therefore, larger spring ranges are possible at the same pressure (resilience). Gentle, low-frequency seat movements as well as greater seating comfort are thus produced.
If the vehicle travels for example over an unmade and uneven region, it is conceivable for the additional volume means not to be connected, so that direct impact against an element at the end of the range of the spring is prevented. Such a force/displacement characteristic line is shown in FIG. 1A (“K” stands for force and “W” stands for displacement), from which it can be seen that at the impact point A1 or up to the impact point A1, the air spring continuously deflects within the force/displacement characteristic line in accordance with a presettable gradient. This provides the advantage of greater resilience in the case of strong excitation and makes it possible for a driver to prevent disadvantageous and uncomfortable sudden impacts against the element at the end of the range of the air spring when the air spring completely deflects.
However, such a steep setting of the characteristic line, for example by disconnecting the additional volume means from the air spring, generally reduces comfort in normal driving operation and for example provides worse “SEAT values”, that is to say measured values relating to individual physical measured variables and the effects on the passengers associated therewith.
If, for example, the vehicle then travels over a made road which is not greatly uneven, the force/displacement characteristic line may become shallower owing to the additional volume being connected to the air spring, so that the air spring can deflect more softly, thereby significantly increasing comfort in normal driving operation. However, on the other hand this is disadvantageous in that if there is an unexpected pothole on the made road, when driving over the pothole, extremely high spring ranges are covered with such strong excitation, and there is the risk that if the impact point A1 is suddenly reached, the deflection is abruptly stopped, thereby causing a sudden increase in the force acting on the passengers in the vehicle (see FIG. 1B).